The present invention relates an appearance inspection apparatus for a flat tablet which picks up and fetches an image of the front surface, the reverse surface and the overall side face of a flat tablet, processes the thus fetched images to detect whether or not the flat tablet has an unacceptable appearance, and separately recovers unacceptable tablets having an unacceptable appearance and acceptable tablets having no unacceptable appearance.
Conventionally, an appearance inspection for inspecting whether or not a tablet suffers from a defect such as sticking of a foreign article or soiling to the tablet, deformation of the tablet such as a cut or a crack, or a defective print is automatically performed using an appearance inspection machine.
Conventionally, when an appearance inspection machine is used to automatically inspect a pharmaceutical tablet having a flattened shape (hereinafter referred to simply as “flat tablet”), the following method is generally used. In particular, flat tablets supplied at random are aligned and transported in a predetermined form. Then, during the transportation, the posture of each of the flat tablets is successively changed to an uprightly erected posture having a diametrical direction thereof directed in the vertical direction, a horizontally lying posture wherein the thickness-wise direction of the flat tablet is directed in the vertical direction and another horizontally lying posture wherein the front and reverse surfaces are directed reversely in the vertical direction. Every time each of the flat tablets assumes a different one of the postures, an image of the flat tablet is picked up. Consequently, a front surface image, a reverse surface image and a side face image of each of the flat tablets are fetched, and the thus fetched images are processed to detect whether or not the flat tablet has an appearance defect. It is to be noted that, although ordinary flat tablets do not specifically have a front surface and a reverse surface, in the present specification, the surface of a tablet whose image is picked up first is referred to as “front surface” while the other surface of the tablet whose image is picked up later is referred to as “reverse surface”.
Conventionally, as one of such appearance inspection machines of the type described, the following apparatus inspection machine is known (refer to, for example, Japanese Patent Laid-Open No. 2001-33392). In particular, a plurality of transport drums are disposed such that the outer circumferential faces thereof are positioned close to each other, and flat tablets are held on the outer circumferential faces of the transport drums and transported successively by the drums while successively being delivered between the drums. During the transportation, such posture changes of each flat tablet as described above are performed to successively pick up images of the tablet in an upright posture, a horizontally lying posture and another horizontally lying posture with the front and reverse surfaces reversed.
However, the apparatus which is configured such that the posture changes of each flat tablet are performed while it is transferred between a plurality of transport drums to fetch images of the flat tablet in various postures in this manner is disadvantageous in that the transport path becomes extremely complicated inevitably and much advanced control is required for the speeds of rotation and synchronism adjustment and so forth of the drums, resulting in complication of the apparatus.
Further, a delivering operation between transport drums results in application of a high load to a tablet, and therefore, a cut or a crack is liable to occur with the tablet. In this instance, occurrence of a cut or a crack not only makes the tablet an unacceptable tablet, but causes sticking of a fraction of powder produced as a result of such cut or crack to another normal tablet. Therefore, there is the possibility that the normal tablet may be detected as an unacceptable product in error.